Fluid pressure booster and fluid pressure brake apparatus having the same

Abstract

A fluid pressure booster and a fluid pressure brake apparatus having the same are provided. The fluid pressure booster includes an auxiliary fluid pressure source having a pump and a pressure accumulator, a pressure adjusting device which adjusts fluid pressure supplied from the auxiliary fluid pressure source to a value corresponding to an operating amount of a brake operation member by displacement of a spool valve and introduces the same into a boost chamber, a boost piston which receives the fluid pressure introduced into the boost chamber to generate assist force and operates a master piston of a master cylinder by assisted force, and a displacement absorption member which is provided at a position to which thrust force of the master piston is applied, and which is compressed in an axial direction when transfer power between the boost piston and the master piston exceeds a setting value.

1 . A fluid pressure booster for a fluid pressure brake apparatus, comprising:
 an auxiliary fluid pressure source including a power-operated pump and a pressure accumulator;   a pressure adjusting device which adjusts fluid pressure supplied from the auxiliary fluid pressure source to a value corresponding to an operating amount of a brake operation member by displacement of a spool valve and introduces the adjusted fluid pressure into a boost chamber;   a boost piston which receives the fluid pressure introduced into the boost chamber to generate assist force and operates a master piston of a master cylinder by assisted force; and   a displacement absorption member which is provided at a position to which thrust force of the master piston is applied, and which is compressed in an axial direction when transfer power between the boost piston and the master piston exceeds a setting value.   
     
     
         2 . The fluid pressure booster according to  claim 1 , further comprising:
 a maximum reaction force regulation mechanism which allows the axial compression of the displacement absorption member when the fluid pressure of the boost chamber is lower than the fluid pressure of the auxiliary fluid pressure source and regulates an increase in an amount of the axial compression of the displacement absorption member when the fluid pressure of the boost chamber is equal to or higher than the fluid pressure of the auxiliary fluid pressure source.   
     
     
         3 . A fluid pressure brake apparatus comprising:
 the fluid pressure booster according to  claim 1 ;   a brake operation member which applies brake operating force to the fluid pressure booster;   a master cylinder having a master piston which is operated while being assisted by the fluid pressure booster;   a wheel cylinder which generates braking force by fluid pressure supplied from the master cylinder;   a reflux-type pressure adjusting unit including a pressure decrease solenoid valve which enables the fluid pressure of the wheel cylinder to flow out, a pressure increase solenoid valve which introduces the fluid pressure into the wheel cylinder, and a reflux pump which pumps up brake fluid having flown out from the wheel cylinder via the pressure decrease solenoid valve and thus refluxes the same to a fluid pressure path extending from the master cylinder to the wheel cylinder; and   an electronic control unit which determines whether it is necessary to decrease pressure of the wheel cylinder and whether it is necessary to re-pressurize the wheel cylinder and outputs an operating command to the pressure decrease solenoid valve and the pressure increase solenoid valve.   
     
     
         4 . The fluid pressure brake apparatus according to  claim 3 ,
 wherein the displacement absorption member is formed by an elastic member which can be compressed in an axial direction of the boost piston.   
     
     
         5 . The fluid pressure brake apparatus according to  claim 4 ,
 wherein initial load of the elastic member has a magnitude, with which the elastic member is not compression-deformed when the master cylinder pressure is equal to or lower than a lowest operating pressure of the reflux-type pressure adjusting unit.   
     
     
         6 . The fluid pressure brake apparatus according to  claim 3 ,
 wherein the displacement absorption member is interposed on a power transmission path between the boost piston and the master piston.   
     
     
         7 . The fluid pressure brake apparatus according to  claim 6 ,
 wherein the master piston is formed with a guide hole which is opened at an end face of a side facing the boost piston,   wherein a plunger which receives driving force from the boost piston via a power transmission member is inserted into the guide hole to be slidable in the axial direction, and   wherein the displacement absorption member is interposed between the plunger and a wall surface of an inner end of the guide hole.   
     
     
         8 . The fluid pressure brake apparatus according to  claim 3 ,
 wherein a reaction force provision member which generates reaction force corresponding to an operating amount of the brake operation member and applies the same to the brake operation member and has a jumping characteristic is interposed on a power transmission path between the boost piston and the master piston, and   wherein the displacement absorption member is formed by an elastic member having initial load larger than reaction force of a brake operation which is obtained at a position at which a rapid increase in the master cylinder pressure due to the jumping characteristic ends.